Ultrasonic flow meters are well known for measuring volumetric flow of liquids and gas. Ultrasonic meters may be mounted within a pipe, mounted within a spool piece, or clamped onto the outer surface of the pipe. While ultrasonic meters are suitable and in some case accurate flow meters, such as gas custody meters, ultrasonic meters are not suitable for all fluid flows. For instance, ultrasonic meters have difficulty measuring volumetric flow rate when measuring aerated fluids. The gas bubbles scatter the ultrasonic waves and therefore, provide an inaccurate or no output at all.
Similarly, an array-based flow meter that uses an array of sensors disposed along the pipe for measuring vortical disturbances and/or acoustic waves propagating through the flow, are suitable for some applications and not as suitable for other applications. The array-based flow meter and the ultrasonic meter have common applications that are both suitable for use, however, in other instances, the ultrasonic meter functions better than the array-based meter in some applications and the array-based flow meter functions better than the ultrasonic meter in other applications. The present invention combines the two technologies into a single flow meter to provide a flow meter capable of functions in a great number of applications than each flow meter can function alone.